Dynamic clamping induces rotation-to-beating transition of pinned filaments in gliding assays

We used numerical simulations to investigate how properties of motor proteins control the dynamical behaviour of driven flexible filaments. A filament on top of a patch of anchored motor proteins is pinned at one end, a setup referred to as a spiral gliding assay. There exists a variety of motor proteins with different properties. We found that when these properties are changed, this system generally can show three different regimes: (i) fluctuation, where the filament undergoes random fluctuations because the motors are unable to bend it, (ii) rotation, in which the filament bends and then moves continuously in one direction, and (iii) beating, where the filament rotation direction changes over time. We found that the transition between fluctuation and rotation occurs when motors exert a force sufficient to buckle the filament. The threshold force coincides with the second buckling mode of a filament undergoing a continuously distributed load. Moreover, we showed that when motors near the pinning point work close to their stall force, they cause dynamic clamping, leading to the beating regime. Rather than being imposed by experimental conditions, this clamping is transient and results from the coupling between filament mechanics and the collective behaviour of motors.